--- a/dom/media/mediasource/TrackBuffer.cpp
+++ b/dom/media/mediasource/TrackBuffer.cpp
@@ -206,17 +206,17 @@ TrackBuffer::AppendData(LargeDataBuffer*
   } else if (!hadCompleteInitData && gotInit) {
     MOZ_ASSERT(mCurrentDecoder);
     // Queue pending decoder for initialization now that we have a full
     // init segment.
     decoders.AppendElement(mCurrentDecoder);
   }
 
   if (gotMedia) {
-    if (mLastEndTimestamp &&
+    if (mParser->IsMediaSegmentPresent(aData) && mLastEndTimestamp &&
         (!mParser->TimestampsFuzzyEqual(start, mLastEndTimestamp.value()) ||
          mLastTimestampOffset != aTimestampOffset ||
          mDecoderPerSegment ||
          (mCurrentDecoder && mCurrentDecoder->WasTrimmed()))) {
       MSE_DEBUG("TrackBuffer(%p)::AppendData: Data last=[%lld, %lld] overlaps [%lld, %lld]",
                 this, mLastStartTimestamp, mLastEndTimestamp.value(), start, end);
 
       if (!newInitData) {
@@ -251,21 +251,22 @@ TrackBuffer::AppendData(LargeDataBuffer*
     mInitializationPromise.Reject(NS_ERROR_FAILURE, __func__);
     return p;
   }
 
   if (decoders.Length()) {
     // We're going to have to wait for the decoder to initialize, the promise
     // will be resolved once initialization completes.
     return p;
-  } else if (gotMedia) {
-    // Tell our reader that we have more data to ensure that playback starts if
-    // required when data is appended.
-    mParentDecoder->GetReader()->MaybeNotifyHaveData();
   }
+
+  // Tell our reader that we have more data to ensure that playback starts if
+  // required when data is appended.
+  mParentDecoder->GetReader()->MaybeNotifyHaveData();
+
   mInitializationPromise.Resolve(gotMedia, __func__);
   return p;
 }
 
 bool
 TrackBuffer::AppendDataToCurrentResource(LargeDataBuffer* aData, uint32_t aDuration)
 {
   MOZ_ASSERT(NS_IsMainThread());